Washington is calling for its Nato partners to do more to combat the heroin trade in Afghanistan and is considering reopening the debate over aerial spraying, according to a US official.

The move comes in a week in which heads of state and government at the Nato summit in Bucharest set out their “strategic vision” for Afghanistan in a text that made only passing reference to narcotics.

Thomas Schweich, the number two at the US state department’s bureau of international narcotics and law enforcement affairs, said Afghan poppy production could decline this year after a series of record-breaking harvests – but if it failed to do so, the US would look at spraying again.

“By June-July, after the cultivation and eradication seasons, we will get an idea of whether what we did was good enough,” he said. “We could see a reduction in cultivation. But if we see another increase it would be irresponsible not to raise the issue [of aerial spraying] again.”

Such a move would be controversial. In January, David Johnson, Mr Schweich’s superior, told the Senate’s foreign relations committee that the US had developed plans for aerial eradication. But he added: “We don’t have the capability to do any spraying, and we don’t plan to because we’ve consulted the government of Afghanistan and they do not wish us to.”

Many of the US’s Nato partners argue that aerial spraying would alienate Afghan farmers at a time when the alliance is trying to win hearts and minds in the country.

US officials say that the Nato force in Afghanistan can do more, despite rules on engagement that prevent it from direct eradication of poppy fields itself – restrictions that do not apply to the separate US-led force in the country. “There are a lot of things you can do to help,” said Mr Schweich.

“You can enable missions through intelligence, increasing security, the movement of equipment. Most of all, you need political will.”

But Mr Schweich ruled out co-operation with Tehran in an effort against the Afghan druglords, even though Iran has more than 1m drug addicts, partly because of drug routes from Afghanistan. “The US has very many problems with Iran and until they are resolved we are not going to be dealing with them on the drug issue.”